Sweep circuit for cathode-ray tubes



Sept. 2l, 1948. M. EBYRNE swEEP CIRCUIT FOR cATHoDE RAY TUBES `Filed Sept. 14. 1943 I i Alva-rae Mue/CE .E 5 WQNE Patented Sept. 21, 1948 Std/EEP :CIRCUIT fFGB CATHQDE -RAY TUBES Maurice E.,Byrne, United .StatesArmm Lewiston, Idaho Application September 14, 1943, Serial'No. 502,271

(llaims. (Cl..31 5-9') (Granted Iunder the act of `March 3, 1883, as

amended April i311, 1928; 370 O. G. A757) vThe,invention described herein may be .manuactured and used by ,Crier the Government for governmental purposes, without the 'payment to meofany,royaltythereon.

2 tuned. 'The .output of tuned circuit T--I is Ycon-u nected `to the grid ll of a cathode ray tube i2, while Vthe output of tuned circuit 1F- 2 is con-- nected lto the horizontal deecting plates i3.

This Vinvention relates to radio circuits, parm 5 The wave form meant to bestudiedis applied to ticularly to sweep circuits of a cathode ray tube. the vertical plate Hi in the usual manner.

One object Aof 'this invention is 'to provide a Since tube 'l2 lis suggested as an additional or oircuitiorgmagnifying one portion of the sweep monitor tube, a portion ofthe pulse applied to circuitof anoscilloscope. the ,grid I5 of tube 5 is fed by 4lead l@ to the Another .object is to provide -a lcircuit which vertical plate Il of the main cathode ray tube `Will permit thechoice of a portion of a cathode i8 so that an indication of the portion of sweep ray tube ysweep that magniiies on an auxiliary osbeing investigated will be given. cilloscope. For the purpose of illustration, the following vStill another object is `to vprovide a circuit in operation is described as used with a radio object which the portion ofthe sweep chosen for m-agl5 locating system, in which succession of short ni'cation is adjustably selected. .pulses `are transmitted, the reflection appearing Other objects of my invention will Abe apparent on a cathode ray oscilloscope: from 'the annexed description, at the end whereu At steady state the grid 'i9 of tube 2 is at the of `the novel features of my invention will be same potential as `its cathode 2D so that tube specifically pointed out and claimed. 2 'is normally conducting while tube l is biased In the drawings: to cutoff. `Since tube l is at cutoff, capacitor 2.2i

Figure '1 is a circuit diagram. is :fully charged. A portion of the succession of Figure 2 illustrates the wave :shapes as they keying pulses :is applied to the grid 'l of tube appear at various 'indicated portions of the .cirn ,A positive pulse applied to grid *I raises tube .i cuit. above cutoff and plate 4current starts `flowing.

'In that embodiment of my ,invention which has "been selected for illustration there vare shown six triodes"orithree-element electric tubes marked "I "to B, respectively. Tubes! and 2 and connectingcomponents constitute a multi-vibrator type generator Vof vrectangular voltage pulses. This circuit is activated upon the application of a pulse `from y'outside source 'to the grid of tube 1. Resistor yforming the grid resistor ofA tube A2, is adjustable and its adjustments rwill be ex- 1 plained later 'in a ydescription of fthe operation ofthe entirecircut.

In the .platecircuit of tube 2 forming the output Iof the square wave generator, and coupling network to fthe :next stage, is capacitor .9 `and resistor I0. The value of these ycomponents is such as to create :a short -time :constant so as to produce `short pulses `at each change of direction ofthe -square wave output :from `:tube 2.

`Tube 3 -is a @linear famplier. 'Tube 4 in the following 'stage is Fbiased "highly `negative. The positive-going portion :of pulse output'from tube 3-will `raise lthe gridof tube f4 above cutoff. The output .at this .point is a Vsingle recurrent short pulse :or pip which is applied to the grids 'of tubes 5 andtpconnected in parallel.

'In 1theca'thode circuitsof tubes 15 and 5 `.are azpair of similar'damped tube circuits, T-l and 'IF-12. .Circuit T--i is tuned vto .a frequency double :that frequency to .which circuitT--2 .is

` versed and also yoccurring instantaneously ydrives tube il *back `to `cutoc and tubei. to 'maximum current. After the `second cycle, the ltubes are at normal and nothing can occur until another 'positivejpulse is received .on vthe grid of tube l.

.The .time taken forthe `charge on capacitor 2d to leak off `to a :potential where tube .2 will start conducting is regulated vby varying lre- Zsister-.8.

.As seen iin Figure 2 the ,output of tube 2 is .a lwave which Alhas a xed iront occurring in synchronsm with the applied .positive pulse `to "grid, l while the Y.rear of the wave is adiustably The ldierential coupling network of capacitor .i9 and resistor im .connected :to :the plate `circuit of tube 2 produces a short pulse at eachchange of direction of the square wave output of tube 2. The short pulse produced at the beginning of the square wave output is positive in nature While that produced at the end of the square wave is negative as indicated in Fig. 2. Consequently, the negative going part of the voltage applied to the grid of tube 3 may be moved along the axis in time. This negative pulse at grid of tube 3 will appear as a positive pulse on the grid of tube 4, raising tube 4 above cutoff. Consequently, the output of tube 4 is a single recurrent pulse or pip, negative in character as illustrated in Fig. 2, and selectively variable in time with respect to the keying pulse.

This wave having a steep front is fed to tubes 5 and 6 containing the damped tuned circuits T--I and T-2. Each of tubes 5 and 6 is normally conducting. The current flow in each tube is suddenly cut off as a result of the negative pulse from tube li applied to the grid, and the field in each inductance suddenly collapses. Thus the steep wave front shocks the tuned circuits into oscillation by the inductahce capacitor exchange.

The value of resistor 22 is such as to damp out the oscillation of tuned circuit T-I after one cycle, while the resistor 23 has a value which will damp out the oscillation in tuned circuit T-Z after one half cycle.

The output of tuned circuit T--I is applied to the grid H of cathode ray tube I2, so as to cause brilliance on the positive half cycle and blackout on the negative half cycle. The output of tuned circuit T--Z applied to the horizontal deilecting plate i3 of cathode ray tube i2 is the sweep frequency. Since the last half of the sweep cyclel is blacked out by the grid, only one quarter of the total alternation is visible and the return is eliminated.

A frequency may be selected for instance, which will make visible a distance of one mile of range of the radio object locating system. Control resistor 8 is varied selecting in time that portion of the main sweep desired to be expanded for study. The portion of pulse taken from grid of tube 5, fed to the vertical plates of the main cathode ray tube I 8 gives an indication of that portion of the Wain sweep selected for magnication. In the radio object locating system this will be the time when the reilected pulse or pip occurs.

The keying pulses applied to grid 1 of tube I occur synchronously with the sweep frequency cycles of the main cathode ray tube I8 in a manner Well known to those skilled in the art.

Thus we may select any portion of the main sweep desired, apply it to the additional oscilloscope I2, and through magnification of that portion, carefully study the detailed wave shape.

I claim:

1. In an oscilloscope circuit, a generator of square wave electrical impulses, means for variably controlling the duration of said square wave impulses, a circuit means for generating short electrical impulses at the beginning and end of each of said square wave impulses, a iirst tuned circuit and a second tuned circuit tuned to a frequency' different from said rst tuned circuit, means for applying at least one of said short pulses to said rst and second tuned circuits whereby said tuned circuits are shocked into oscillation, and a cathode ray tube, of which the grid is connected to said first tuned circuit and one set of deecting plates is connected to said second tuned circuit.

2. The method of expanding a portion of the indication on a cathode ray tube which includes applying a -desired signal to a deecting plate of a rst cathode ray tube, generating a pulse of electrical energy synchronously with the sweep frequency of said first cathode ray tube, adjusting the duration of said pulse, passing said pulse through a differentiating circuit thereby generating a short pulse at the beginning and end of said main pulse, applying at least one of said short pulses to a first tuned circuit and a second tuned circuit tuned to a frequency different from said first tuned circuit thereby shocking said iirst and second tuned circuits into oscillation, applying the output of said first tuned circuit to a second cathode ray tube as brilliance control and the output of said secy ond tuned ycircuit as sweep frequency and applying a portion of said desired signal to said second cathode ray tube for study.

3. Means for providing a magnified indication of a portion of the sweep of an object-detecting system comprising, a rst cathode ray tube, a second cathode ray tube, a circuit' including a single-shot multivibrator to which a succession of keying pulses are fed and which is adapted to provide a square wave, a manuallyadjustable control element connected into circuit with said multivibrator and controlling the width of said square wave so that the frontrise on said square wave occurs in time in synchronisrn with the applied keying pulse and the rear drop of said square wave is selectively variable in time for a continuous interval from zero until the next wave starts, a coupling network which produces short pulses of peak waves .at each change of direction of the square wave output, a linear amplifier connected to receive the output of said coupling network, a triode with grid biased highly negative connected to the output of said amplifier, the output of which is a series of pulses comprising only one side of the output wave from said amplifier, a connection between the plate circuit of said triode and the vertical deflecting plates of said main cathode ray tube whereby there is provided in said first cathode ray tube a visual indication of the position along the sweep which the second cathode ray tube is working on, a first damped tuning circuit connected to the output of said triode, a connection between the rst damped tuned circuit and the grid of said second cathode ray tube to cause brilliance on the positive half cycle and blackout on the negative half cycle, a second tuned circuit conriected to the output of said triode and critically damped to pass only one half cycle of each pulse and a connection between said second tuned circuit and said second cathode ray tube, whereby the sweep of said second cathode ray tube represents one magnified portion` of the sweep of said first cathode ray tube.

4. In a radio-operated object-locating device having a main cathode ray tube,'an` auxiliary cathode ray tube arranged to give a magnified indication over a portion of the area covered by said main cathode ray tube, a first damped tuning circuit connected to the grid of said auxiliary cathode ray tube, a second damped tuning circuit having half the frequency of said iirst damped tuning circuit and connected to the sweep deecting plates of said auxiliaryy cathode ray tube, a square wave generator arranged to produce oscillations in response to keying impulses, a selectively variable control element connected to said generator soas to vary the time a succession of keying impulses are fed anda which is adapted to provide a square wave, means` for controlling the width of said square wave so that the front rise on said square wave occurs in synchronism with the applied keying pulse and the rear drop of said square wave is selectively variable in time for a continuous interval from zero until the next Wave starts, a coupling network which produces short pulses of peaked waves at each change of direction of the square wave output, an amplifier connected to receive the output of said coupling network, an electron tube having a control grid biased to cut oii' connected to the output of said amplifier, a connection between said electron tube and the vertical deiiecting plates of said first cathode ray tube whereby there is provided in said iirst cathode ray tube a Visual indication of the position along the sweep which said second cathode ray tube is displaying, a iirst damped tuned circuit connected to the output of said electron tube, a connection between the first damped tuned circuit and the grid of said second cathode ray tube to cause brilliance on the positive half cycle and blackout on the negative half cycle, a second tuned circuit connected to the output of said electron tube and damped to pass only one half cycle of each pulse, and a connection between said second tuned circuit and said second cathode ray tube whereby the sweep of said second cathode ray tube represents one magnied portion of the sweep of said rst cathode ray tube.

. MAURICE E. BYRNE.

REFERENCES CITED The following references are of record in the i file of this patent:

UNITED STATES PATENTS Number Name Date 2,063,025 Blumlein Dec. 8, 1936 2,085,402 Vance June 29, 1937 2,088,495 Swedlund July 27, 1937 2,139,432 Andrieu Dec. 6, 1938 2,186,388 Moritz, Jr Jan. 9, 1940 2,193,868 Geiger Mar. 19, 1940 2,215,197 Sherman Sept. 17, 1940 2,241,256 Gould May 6, 1941 2,244,513 Burton June 3, 1941 2,275,460 Page Mar. 10, 1942 2,355,363 Christaldi Aug. 8, 1944 

